Universal Media Disc
UMD can also mean University of Maryland.
The Universal Media Disc (UMD) is an optical disc made by Sony for their PlayStation Portable handheld console. It can hold up to 900 megabytes (single layer) or 1.8 gigabytes (double layer) of data. The disc can store games, music, and video, along with updates for the PSP. It is the first optical disc format to be used for a handheld video game system. To prevent illegal copying, Sony has not made blank discs available for sale. This disc is not used with any other devices. The UMD is very fragile and can be broken from misuse.